CN1385359A - Carbon nano tube film micromechanical infrared detector - Google Patents

Abstract

The invention discloses a carbon nanotube thin-film micromechanical infrared detector with simple structure, high resolution, wide spectral response range, high sensitivity, low cost and simple process, including micromechanics of a certain base material, and a pick-up circuit. , a layer of carbon nanotube film is grown on the micromechanical resonator. As a light radiation absorbing material, the absorption coefficient η of the carbon nanotube film to infrared radiation can reach 0.98, so that it has high sensitivity and small noise equivalent power. , in order to improve the detection ability of this kind of detector. The microresonator is made by MEMS processing technology, which can be mass-produced, thereby reducing the cost of the device.

Description

Carbon Nanotube Thin Film Micromachined Infrared Detector

1. Field

The invention relates to an infrared detector, in particular to a carbon nanotube film micromechanical infrared detector on which a micromachine is made on a substrate of a certain material and a carbon nanotube film is grown on it.

2. Background technology

Infrared detection plays an important role in modern science. Various infrared detectors are widely used in many aspects such as imaging, tracking, guidance, reconnaissance, early warning, remote sensing, weak signal detection, radiation measurement, automatic control and laser detection.

Due to the different detection mechanisms, there are two main types of infrared detectors: photon detectors and thermal detectors. Common photon detectors include photoelectron emission detectors, photoconductive detectors, photovoltaic detectors, and photomagnetoelectric detectors. Common thermal detectors include thermistor bolometers, radiance thermocouples and thermopiles, pneumatic detectors, pyroelectric detectors, etc. Pyroelectric detectors are a new type of infrared detectors that work according to the pyroelectric effect. Compared with photon detectors, pyroelectric detectors have a wider spectral response; compared with thermal detectors composed of thermal resistors, thermocouples, and thermopiles, their frequency response is faster, and they can range from low frequencies of more than ten Hz to thousands of Hz. The wide frequency response characteristics of the frequency can even be made into a fast pyroelectric detector with a response time of less than microseconds. Usually it is assembled together with field effect transistor impedance converter, and its structure is shown in Fig. 1. 101 is a detector, 102 is a field effect transistor, 103 is a source resistor, and the output signal is drawn from both ends of the source resistor 103 . 104 and 105 are the input resistance and input capacitance of the field effect transistor impedance converter respectively.

The disadvantages of pyroelectric detectors are: 1. The sensitivity is low due to material limitations. 2. Large volume. 3. At higher frequencies, due to the increase in dielectric loss as the frequency rises, the ideal performance is far from being achieved. 4. Higher cost.

3. Contents of the invention

According to the partial defects or deficiencies in the prior art, the purpose of the present invention is to provide a carbon nanotube thin film micromachine with simple structure, high resolution and wide spectral response range, high sensitivity, low cost and simple process. Infrared Detectors.

In order to achieve the above object, the design mechanism of the present invention is: thermal deflection occurs when the micromechanical resonator is irradiated by light radiation, and the natural oscillation frequency f _o (or angular frequency w _o =2πf _o ) of its mechanical structure changes. By measuring the thermal Deflection (static) or measurement of f _o (dynamic) enables the detection of radiant light intensity.

The technical solution adopted is: a carbon nanotube film micromachine infrared detector, including a micromachine 1 of a certain base material, a pick-up circuit 3, and a carbon nanotube film 2 grown on the micromachine 1;

Micromachinery 1 refers to microresonant devices, which can be microcantilever beams, microbridges, and micromembranes (square or round membranes);

The micromechanical resonator includes a base 4, a radiation window 5, a power supply 6, a power supply connection 7 and a power supply connection 8, and an output signal connection 9 and an output signal connection 10;

The pick-up method can be electrical pick-up or optical pick-up. Electric pick-up generally uses the piezoresistive effect of silicon to make a piezoresistor on a micromechanical resonator and connect it to the designed detection circuit. When the device resonates, the piezoresistor The resistance value change is used to test the resonance characteristics of the device; the optical pickup is usually used to realize the vibration measurement of the micromechanical resonator by using the fiber optic sensor technology.

Some other features of the present invention are that the base material is selected from common semiconductor materials, such as silicon, silicon dioxide, and silicon nitride.

The carbon nanotube film 2 can be directly grown on the substrate by catalytic pyrolysis or CVD, or can be formed on the substrate by implantation methods such as electrophoresis, coating, and printing.

The pick-up circuit 3 utilizes the piezoresistive effect of silicon and connects four piezoresistors in the form of a Wheatstone bridge.

A carbon nanotube film is grown on the micromechanical resonator as an optical radiation absorbing material. Since the absorption coefficient η of the carbon nanotube film to infrared radiation can reach 0.98, it has high sensitivity and small noise equivalent power. In order to improve the detection ability of this type of detector.

Micromechanical resonators are manufactured through MEMS processing technology, which can be mass-produced, thereby reducing the cost of the device.

4. Description of drawings

Fig. 1 schematic diagram of pyroelectric detector principle;

Fig. 2 structure diagram of the carbon nanotube thin film silicon micro-cantilever resonator of one embodiment of the present invention;

Fig. 3 is a schematic diagram of the overall structure of a carbon nanotube film silicon micro-cantilever infrared detector according to an embodiment of the present invention.

5. Specific implementation

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, but is not limited to the embodiments.

Embodiment: Refer to Fig. 2 and Fig. 3, Fig. 2 is a structural diagram of a carbon nanotube thin film silicon micro-cantilever beam resonator, including a semiconductor base material 1 and a carbon nanotube thin film 2 grown thereon, and a pick-up circuit 3 . Figure 3 is a schematic diagram of the overall structure of a carbon nanotube thin-film silicon micro-cantilever infrared detector, including a base 4, a radiation window 5, a power supply 6, a power supply connection 7, a power supply connection 8, and an output signal connection 9 and an output signal connection 10.

Micromachine 1 refers to micromechanical resonant devices, which can be microcantilever beams, microbridges, and micromembranes (square membranes or circular membranes), etc.

The pickup method can be electrical pickup or optical pickup. Electric pick-up generally uses the piezoresistive effect of silicon to make a piezoresistor on a silicon micromechanical resonator, connect it to the designed detection circuit, and test the resonance characteristics of the device by changing the resistance of the piezoresistor when the device resonates. Optical pickup is typically implemented using fiber optic sensor technology for vibration measurement of silicon micromechanical resonators.

The present invention is prepared according to the following conventional processes

1. Fabrication of micro-cantilever beam 1

The micro-cantilever is a micro-cantilever structure in which semiconductor materials such as silicon, silicon dioxide, and silicon nitride are used as base materials to form a micro-cantilever resonator. In this embodiment, the base material is silicon. Of course, silicon dioxide, silicon nitride, etc. can be used as base materials to realize micro-cantilever beam structure, micro-bridge and micro-membrane (square or round membrane) structure.

2. Fabrication of pickup circuit 3

The pick-up circuit uses the piezoresistive effect of silicon to connect four piezoresistors into a Wheatstone bridge. In this embodiment, the varistor is formed by expanding boron on the front side of the semiconductor material silicon, and the aluminum connection plate is used to reverse-engrave the aluminum to form the metal connection, and the connection is led out by the method of gold wire ball pressure welding.

3. Preparation of carbon nanotube film 2

The backside of the silicon base material in the preceding steps is cleaned by ultrasonic cleaning with acetone, alcohol, and deionized water, and then carbon nanotubes can be grown by many methods. Such as catalytic pyrolysis method, CVD method directly grow on the base material, and can also be formed on the base material by electrophoresis, coating, printing and other transplantation methods.

4. Instrument assembly

After the above steps are completed, the carbon nanotube thin film silicon micro-cantilever infrared detector is obtained, and fixed on the base, as shown in Figure 3, the infrared detection can be performed.

Claims (4)

1. A carbon nanotube film micromechanical infrared detector, characterized in that: a micromachine [1] comprising a certain substrate material, a pick-up circuit [3], and a carbon nanotube film [2] grown on the micromachine [1] ]; Micromachinery [1] refers to microresonant devices, which can be microcantilever beams, microbridges, and micromembranes, etc.; The micromechanical resonator includes a base [4], a radiation window [5], a power supply [6], a power connection [7] and a power connection [8], and an output signal connection [9] and an output signal connection [10 ]; The pick-up method can be electrical pick-up or optical pick-up. Electric pick-up generally uses the piezoresistive effect of silicon to make a piezoresistor on a silicon microresonator and connect it to the designed detection circuit. When the device resonates, the piezoresistor The resistance value change is used to test the resonance characteristics of the device; the optical pickup is usually used to realize the vibration measurement of the silicon microresonator by using the fiber optic sensor technology. 2. The carbon nanotube film micromechanical infrared detector according to claim 1, characterized in that: the base material is selected from common semiconductor materials, such as silicon, silicon dioxide, and silicon nitride. 3. The carbon nanotube film micromechanical infrared detector according to claim 1, characterized in that: the carbon nanotube film [2] can be directly grown on the substrate by catalytic pyrolysis or CVD, or can be Formed on the substrate by electrophoresis, coating, printing and other implantation methods. 4. according to the described carbon nanotube film micromachine infrared detector of claim 1, it is characterized in that: described pick-up circuit [3] utilizes the piezoresistive effect of silicon, and four piezoresistors are connected into Wheatstone bridge form .

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